Fracture strength of chemically vapor deposited diamond on the substrate and its relation to the crystalline structure

The mechanical strength of chemically vapor deposited diamond is characteri zed in terms of fracture toughness. The toughness of film and adhesion inte rface to the substrate were independently measured using techniques recentl y developed by the authors. In this paper, diamond was deposited by microwa ve plasma chemical vapor deposition using a variety of deposition condition s. The fracture toughness of the interface initially increased and then dec reased with increasing amounts of methane in the source gas mixture. On the contrary, the toughness of the films was simply found to decrease with res pect to the increment of methane concentration. This interesting trend of t oughness was explained by the crystalline structure of the deposited diamon d. (C) 2000 Elsevier Science S.A. All rights reserved.